Re: libevent wrapper

On Friday 28 November 2008 09:57:02 Antony Dovgal wrote: > On 28.11.2008 09:59, Arnaud Le Blanc wrote: > > I just found a problem when an event resource is deleted while the callback is > > called (event_free() allows that). > > Right, that's exactly why I do zend_list_addref(event->rsrc_id); Yes, but event_free() does zend_list_destroy(event->rsrc_id). Actually I experienced this problem with a buffer event. Say you have something like this: my_bufferevent_write_callback($buffev_resource, $myarg) { if ($some_condition) { event_buffer_free($event); } } This decrements the refcount of the resource, and in my test script the resource was then destroyed in _php_bufferevent_writecb on the line "zval_ptr_dtor(&(args[0]));" See [1] for a reproduce script (with USE_ZEND_ALLOC=0 valgrind shows the problem). [1] http://arnaud.lb.s3.amazonaws.com/reproduce1227866439.php > > > It is possible to change the internal > > callback functions so that they do not need to use the the possibly freed > > memory after the call. This also makes them simpler by not attempting to avoid > > freeing the resources. The same problem applies for buffer and loop resources. > > I made a patch for that [1] > > I'm afraid I don't understand a half of it. See the patch on the "_php_bufferevent_writecb" chunk. Basically the change is that the function will never [need to] read bevent after call_user_function(). It also removes all attempts to avoid the destruction of the resources (base and the buffer event itself) as this is not anymore needed. > > >(for loops I had to add a counter of attached > > events and to fail in event_base_free() when the counter is > 0). > > I don't think it's correct - each event does zend_list_addref() for the base > when the base is set and zend_list_delete() when the event is destroyed, so base > should have refcount == 1 after all events are destroyed. Except if you do event_base_free($base) ;) The refcount prevents PHP from feeing the resource. The counter I added prevents the user from artificially decrementing the refcount when the loop base has events attached to it. Regards, Arnaud